The activity chosen is called the overhead allocation base or simply the base. The base chosen should be the one most closely related to the cost being allocated; that is, the one that appears to drive most of the factory overhead. If no single base drives most of overhead cost, than multiple bases may be used-one for each singnificant activity, or one for each cost center, or one for each activity within each cost center. For brevity in this introduction, a single base will be used.